Close the sqlite connections tests leaked

[ajslater]

Summary

A coverage-enabled make test reported 12 ResourceWarning: unclosed database in <sqlite3.Connection> warnings, attributed to test_metron_id_attribute_fallback.py and test_write_api.py. That attribution is only where garbage collection happened to run; it moved between runs.

To find the openers, a throwaway pytest plugin (not committed) swapped in a sqlite3.Connection subclass that records the opening test and stack, and logs any connection collected while still open. It traced all 12 to three test files. None is a production leak:

File	Leaks	Cause	Fix
tests/unit/test_vacuum.py	6	with sqlite3.connect(...) commits on exit but never closes	closing(...). The small-file test now opens in autocommit, as _make_bloated_db already does, so its writes still land without the old implicit commit
tests/unit/test_cover_hash.py	4	three tests never closed their CoverHashUrlCache; one read the table back via a bare with sqlite3.connect	cache.close() (the file's existing convention) and closing(...)
tests/unit/test_quota_reserved_skip.py	2	search() builds the shared Metron session before the gate check under test, which opened mokkari's SqliteCache (no close() in 4.9.0)	stub _get_session in the shared _source helper, as test_a_healthy_budget_records_no_reason already did

Hermeticity hole found along the way

The two quota tests opened the developer's real ~/.cache/comicbox/online/metron_cache.sqlite. OnlineSettings() built directly in a test has cache.dir=None, which resolves to the platformdirs cache. The conftest pins COMICBOX_ONLINE__CACHE__DIR, but only config-loaded settings read that variable. After this change no test in the suite opens a sqlite file under the real home cache (checked with the same plugin). The hole itself is still there for future tests that build OnlineSettings() directly.

Test plan

• make test on current develop + this commit: 2390 passed, 1 skipped, 0 ResourceWarning (was 12). The 5 remaining warnings are pymupdf's SWIG DeprecationWarnings, which predate this change.
• Tracking plugin over the full suite: 0 connections collected while open, 0 opens under the real home cache
• make fix (no changes), make lint, make ty clean

🤖 Generated with Claude Code